Predation, habitat drying, and habitat size and production of vector mosquitoes

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DESCRIPTION (provided by applicant): Vector mosquitoes from container habitats are important as bridge or zoonotic vectors for multiple North American encephalitis viruses, including West Nile Virus and LaCrosse Encephalitis Virus. General theory for ecology of freshwater systems leads to the hypothesis that production of adults should be affected by size of containers directly, and that container size should affect hydroperiod, which will affect adult production directly, and indirectly as it affects the number and kinds of predators of mosquitoes in these systems. Impacts of predators in these systems are likely to interact with density dependent mortality, producing in some circumstances compensatory or overcompensatory mortality, wherein predation yields equal or greater production of adult mosquitoes, respectively, than observed in the absence of predation. Predators may also have nonlethal effects on mosquito prey via induction of costly behavioral changes. All of these effects indicate that knowledge of production of particular vectors from man-made containers can be important for efficient targeting of containers for source reduction or larviciding. The proposed research will test for these direct and indirect effects across a broad range (0.035 - 350 L, four orders of magnitude in volume) of artificial container volumes. The proposed research uses field and laboratory experiments to achieve four specific aims: 1) Quantifying the relationships among container size, hydroperiod, predator abundance, larval abundances, and adult production and diversity of important container-dwelling vectors in the Midwest. 2) Separating experimentally the direct and indirect effects of container size, hydroperiod, and predation by manipulating hydroperiod or predation, independent of container size. 3) Determining patterns of compensating and overcompensating mortality caused by predators across a range of different container sizes. 4) Determining the likelihood of some important indirect nonlethal effects of predation on mosquito production, particularly slowed development and growth of larvae, or reduced longevity, feeding success, and fecundity of adults, which may be induced by behavioral changes that reduce risk of predation. The proposed research will yield a better understanding of how habitat scale and characteristics affect production of vectors from containers and which container sizes are likely to produce particular vector species, and thus how best to target particular sorts of containers for reducing larval success via source reduction or larviciding to reduce production of adult vectors. PUBLIC HEALTH RELEVANCE: A number of the prominent North American mosquito vectors of encephalitis viruses develop as larvae in man-made containers ranging in size from small bottles to large rain barrels. General theory of ecology of aquatic habitats suggests that habitat size, hydroperiod, and predation interact to influence success of aquatic species, such as these mosquito vectors. This project investigates how these three aspects of the aquatic habitat determine production of adult vectors, and therefore risk of encephalitis. Because these encephalitis vectors are widespread in the eastern US, this research is relevant to questions concerning how to target man made containers for source reduction or larviciding to minimize production of specific vectors.